This invention relates generally to the assembly of trusses, and in particular to a locator for holding a structural member at a predetermined position on an assembly apparatus.
Pre-manufactured structural frameworks, such as trusses, are widely used in the construction industry for forming a roof, wall panel, floor, or other building component. Each truss includes a collection of structural members, typically in the form of wooden timbers, held together by connectors, such as connector (“nailing”) plates pressed into the timbers. The truss is assembled to the correct specifications at a factory and then shipped to a construction site. A gantry press apparatus is frequently used to facilitate efficient assembly of the truss. It features a table on which the timbers and connector plates are placed at desired relative positions to form the particular truss configuration.
For many trusses including a floor truss, two end stops are used on the table for setting positions of timbers at opposite ends of the truss and for securely holding the truss during assembly. Each end stop provides a flat surface for engaging a timber. Conventionally, a first end stop is an angle bracket which is fastened at a fixed position along a slot in the table. Timbers are typically laid on the table starting from the first end stop and proceeding toward the opposite end. A second end stop is also fastened to the table at the opposite end and is tightened against the endmost timber. Connector plates are placed at locations where adjacent timbers intersect. A motorized roller apparatus (i.e., the gantry) then travels along the table to press integral teeth of the connector plates into the timbers thereby joining them together. The truss is removed and the process is repeated with a new set of timbers.
Unfortunately, the process of fastening end stops can be inefficient. A worker must lean over the table and adjust the second end stop to be tight against the endmost timber and then tighten a fastener or clamp, typically with a wrench, to lock it in position. After the gantry has traveled along the table, the worker must loosen that fastener and pull away the second end stop before the truss can be removed. Some workers have instead adopted a practice of striking the end stop with a hammer to quickly move or rotate it out of the way for removing the truss, which can damage the apparatus.
Another drawback is that conventional end stops are not flexible for use in assembling trusses of various configurations. Typically, there is a single stop on each end which may not be adequately sized for engaging a timber of a larger truss. Some trusses require, for compatibility with certain house wall arrangements, an offset end having two end timbers at spaced lateral positions. The conventional end stop can engage only one timber, and as a result the assembled timbers are subject to inadvertent shifting as the gantry travels along the table. Further, the end stop is not readily portable to a new location. The worker must use the wrench and loosen the fastener before sliding the end stop along a slot, such as to center the stop along a timber, accommodate a new truss, or to remove the stop for use on another table.
Some flat trusses require an opening (known as a “chase”) between upper and lower chords which is free from other timbers to permit large heating and cooling ducts to pass through the truss. Unfortunately, timbers at sides of the chase can become slightly misaligned when forming these trusses due to build up of timber length tolerances and imperfections. End stops have not typically been used to strengthen the structure at these positions, partially because of the time necessary for installing and removing the stops.